Advertise on Bikeforums.net



User Tag List

Results 1 to 12 of 12
  1. #1
    Doomsled funbun's Avatar
    Join Date
    Aug 2003
    Location
    Tuscaloosa, AL
    My Bikes
    Trek 800
    Posts
    661
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Please explain hill grades to me

    Okay, I don't understand hill grades. 10% grade, 17% grade, it makes no sense to me. Please explain.
    Check it out:

    Blog The Travelogue

  2. #2
    mac
    mac is offline
    They see me rollin' mac's Avatar
    Join Date
    May 2005
    Location
    Los Angeles
    My Bikes
    2005 Cannondale T2000
    Posts
    785
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    WikiPedia is your friend for Grade (geography).

  3. #3
    Senior Member oldokie's Avatar
    Join Date
    Jul 2006
    Location
    Oklahoma
    My Bikes
    Bianchi San Remo, Cannondale SR500
    Posts
    412
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Grade is NOT the same as and angle. Grade refers to the amount os increase in height relative to the horizontal distance. Example...a 5 foot rise over 100 ft is a 5% grade. A 100 ft rise over the same 100 ft (aka...45 degree angle) is a 100% grade
    Inside every old person is a young person wondering what happened.

    06 C'dale SR500
    96 Bianchi San Remo for touring

  4. #4
    Senior Member
    Join Date
    May 2005
    Posts
    108
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by oldokie
    Grade is NOT the same as and angle. Grade refers to the amount os increase in height relative to the horizontal distance. Example...a 5 foot rise over 100 ft is a 5% grade. A 100 ft rise over the same 100 ft (aka...45 degree angle) is a 100% grade
    So? This is like the 'pitch' or slope of a roof?


    Thaks,

    Tim

  5. #5
    Geek Extraordinaire sivat's Avatar
    Join Date
    Feb 2006
    Location
    Long Beach, CA
    My Bikes
    Bianchi Advantage Fixed Conversion; Specialized Stumpjumper FS Hardtail
    Posts
    1,769
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by oldokie
    Grade is NOT the same as and angle. Grade refers to the amount os increase in height relative to the horizontal distance. Example...a 5 foot rise over 100 ft is a 5% grade. A 100 ft rise over the same 100 ft (aka...45 degree angle) is a 100% grade
    This is, apparently, not the international standard. In some countries the grade is the increase in height over the actual distance traveled. In other words, considering a right triangle with the angle of interest from the horizontal to the slope, we use the opposite over the adjacent multiplied by 100, in some other countries they use opposite over hypotenuse times 100. It doesn't make much of a difference, but could be important to know.
    I'd rather have a bottle in front of me than a frontal lobotomy.

    Sintesi Conversion Serotta Track

  6. #6
    Caffeinated. Camel's Avatar
    Join Date
    Aug 2004
    Location
    Waltham, MA
    My Bikes
    Waterford 1900, Quintana Roo Borrego, Trek 8700zx, Bianchi Pista Concept
    Posts
    1,541
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    ...And in some countries they apear to run out of one sign, so they seem to just use another.

    As an example: in Kyrgyzstan, a LOT of what were posted as 6 & 9 % grades were easily 12+. I believe they put up the signs just so the truck drivers know there is a climb/descent ahead of time.
    mmmm coffeee!

    email: jfoneg (_"a t symbol thing"_) yahoo (_"period or dot"_) com

  7. #7
    Punk Rock Lives Roughstuff's Avatar
    Join Date
    Feb 2002
    Location
    western new england
    My Bikes
    Fuji touring
    Posts
    3,008
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Timonabike
    So? This is like the 'pitch' or slope of a roof?


    Thaks,

    Tim
    Yes. But let me clarify some things.

    Strictly speaking, the 'grade' of the road is the vertical RISE for every HORIZONTAL unit of travel. Thus if you climb 264 feet in a horizontal mile, that is a 5% grade because 264/5280 is .05, or 5% Geometry students would refer to this grade as the TANGENT of the angle of ascent.

    Now, to be honest, this is not a realistic way to describe a grade. Instead, most people view the grade as the VERTICAL RISE for every unit of raodway travel. That would be the hypotenuse of the triangle you are envisioning in your mind. Thus in this measure the grade is the SINE, not the tangent, of the angle of ascent.

    But as any 9th grade geometry geek will proudly tell you, for small angles the difference between the TANGENT and the SINE, is very very small.

    Anyone out there..correct me if i have screwed this up, as I don't have my geometry book in front of me just now. But I think I am correct.

    Hopefully I am not playing fast and looses with my hypotenuses!

    roughstuff
    Electric car sales are on fire! :)

  8. #8
    cup
    cup is offline
    Member
    Join Date
    Aug 2006
    Posts
    40
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    grade vs angle vs pitch

    Grade could be considered the same as angle and pitch only it's a very small increment.

    For example a 25% grade (unheard of)would be a 3/12 pitch or an 11.25 degree angle...right?

  9. #9
    Punk Rock Lives Roughstuff's Avatar
    Join Date
    Feb 2002
    Location
    western new england
    My Bikes
    Fuji touring
    Posts
    3,008
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cup
    Grade could be considered the same as angle and pitch only it's a very small increment.

    For example a 25% grade (unheard of)would be a 3/12 pitch or an 11.25 degree angle...right?

    well, if you use tangent, the 'rise over the run,', then the pitch is always correct. If you use SINE, which is the rise over the hypotenuse (the length of the roadway), then yes, it is accurate for only small angles.

    roughstuff
    Electric car sales are on fire! :)

  10. #10
    Senior Member
    Join Date
    Sep 2004
    Location
    Frisco, CO
    My Bikes
    '93 Bridgestone MB-3, '88 Marinoni road bike, '00 Marinoni Piuma, '01 Riv A/R
    Posts
    1,059
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cup
    Grade could be considered the same as angle and pitch only it's a very small increment.

    For example a 25% grade (unheard of)would be a 3/12 pitch or an 11.25 degree angle...right?
    Actually, a 25% grade is not "unheard of". I cycled up a 24% grade in Wales a few years back, and when I proudly told a Brit what I had done I was told that there were roads in Yorkshire as steep as 33%.

  11. #11
    Punk Rock Lives Roughstuff's Avatar
    Join Date
    Feb 2002
    Location
    western new england
    My Bikes
    Fuji touring
    Posts
    3,008
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by markf
    Actually, a 25% grade is not "unheard of". I cycled up a 24% grade in Wales a few years back, and when I proudly told a Brit what I had done I was told that there were roads in Yorkshire as steep as 33%.
    Those grades just freak me out when I see them, even if they are only short 'pops' of a few hundred feet at most. And going DOWN...you keep looking for where the roadway is as you come over the lip of the incline. I have walked down more hills that I have walked up.

    roughstuff
    Electric car sales are on fire! :)

  12. #12
    cup
    cup is offline
    Member
    Join Date
    Aug 2006
    Posts
    40
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by markf
    Actually, a 25% grade is not "unheard of". I cycled up a 24% grade in Wales a few years back, and when I proudly told a Brit what I had done I was told that there were roads in Yorkshire as steep as 33%.

    I would have been thoroughly disappointed if I hadn't got a response to that!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •